fix: use date safely within validation window in organization spec (#5535)

The test used `DateTime.current.next_year - 1.day` which is right at the
boundary of the `issued_at_cannot_be_further_than_1_year` validation.
This causes intermittent failures due to timing precision. Using
`6.months.from_now` keeps the test intent (future date that passes
validation) while staying well within the allowed window.

Author: costajohnt

spec/models/organization_spec.rb

@@ -404,9 +404,9 @@
 
     it 'is the year of the earliest of donation, purchase, or distribution if they are earlier ' do
       freeze_time do
-        create(:donation, organization: organization, issued_at: DateTime.current.next_year - 1.day)
-        create(:purchase, organization: organization, issued_at: DateTime.current.next_year - 1.day)
-        create(:distribution, organization: organization, issued_at: DateTime.current.next_year - 1.day)
+        create(:donation, organization: organization, issued_at: 6.months.from_now)
+        create(:purchase, organization: organization, issued_at: 6.months.from_now)
+        create(:distribution, organization: organization, issued_at: 6.months.from_now)
         expect(organization.earliest_reporting_year).to eq(organization.created_at.year)
         create(:donation, organization: organization, issued_at: 5.years.ago)
         expect(organization.earliest_reporting_year).to eq(5.years.ago.year)